A state appeals court today upheld New Jersey’s use of electronic voting machines, but the judges expressed serious concerns about possible human error and ordered further review of the state’s safeguards.

The ruling, which upheld a lower court decision, is the latest in a legal battle dating back to 2004 when state Assemblyman Reed Gusciora and others sued over the state’s use of the machines. The lawsuit claimed the touch-screen systems, called direct recording electronic voting machines, were unreliable because they didn’t produce a paper backup and were susceptible to hacking.

Then-Gov. Jon Corzine signed legislation in 2005 that would have required all machines to be retrofitted with a paper backup system by January 2008, but that deadline wasn’t met and in 2009 lawmakers suspended it indefinitely over a lack of funding.

State Superior Court Judge Linda Feinberg upheld the use of the machines in 2010 and ordered a review, but stopped short of requiring that they produce a paper backup. During hearings on the issue, the plaintiffs presented evidence including a report by a Princeton University professor that claimed the machines could be hacked into in as little as seven minutes and altered to affect election results.

In today’s decision, the three-judge appellate panel sided with Feinberg’s opinion that the plaintiffs didn’t prove the machines violated voting rights and equal protection statutes. But the judges urged more study on whether the state has adequate safeguards to detect programming errors such as one that compromised an election in Cumberland County in 2011.

In that case, Cynthia and Ernest Zirkle, unsuccessful candidates for Democratic County Committee, complained that votes cast for them were mistakenly tallied for other candidates. An investigation revealed that a county employee had programmed the machines improperly, and a new election was ordered and the Zirkles won.

“We express deep concern as a result of the Zirkle litigation, not as to the fallibility of (electronic voting machines) relative to other voting devices, but rather as to the efforts made by the state to minimize the likelihood of error,” the judges wrote. “It is obvious that but for the very limited pool of voters involved in the Zirkle litigation, the human error that led to completely erroneous election results would never have been detected.”